    (a) Title of the Invention    (b) Cross-Reference To Related Applications    (c) Statement Regarding Federally Sponsored Research or Development    (d) The Names of the Parties to a Joint Research Agreement    (e) Incorporation-By-Reference of Material Submitted on a Compact Disc    (f) Background Of The Invention            (1) Field of the Invention        (2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98            (g) Brief Summary of the Invention    (h) Brief Description of the Several Views of the Drawing(s)    (i) Detailed Description of the Invention    (j) Claim or Claims            Commencing on a Separate Sheet            (k) Abstract of the Disclosure            Commending on a Separate Sheet            (l) Sequence Listing
The invention relates to a storage medium comprising a security feature and a method for producing a storage medium comprising a security feature.
The security features known from the prior art can be formed for example from computer-generated holograms comprising one or more layers of dot matrices or dot distributions which, upon illumination with a preferably coherent light beam, lead to a reconstruction of the information coded in the hologram. In this case, the dot distribution can be calculated as an amplitude hologram, phase hologram or as a kinoform, Fourier or Fresnell hologram. In order to produce computer-generated holograms, the latter are first calculated and then written to a storage medium by means of a suitable writing device by dotwise introduction of energy. The resolution of the resultant dot-matrix can be in the range of down to less than 1 μm. consequently, holograms having a high resolution can be written in a confined space, the information of which holograms can only be read out by illumination with a light beam and reconstruction of the diffraction pattern. In this case, the size of the holograms can be between less than 1 mm2 and plural 1 cm2. A structuring of the type described above can also be referred to as microstructuring.
The computer-generated holograms described above can be combined with directly visible information (microscript, microimages, coded information).
The prior art furthermore discloses a plurality of writing devices for writing computer-generated holograms which write the optical structures of the holograms in planar storage media. By way of example, in this respect reference is made to the documents WO 02/079881, WO 02/079883, WO 02/084404, WO 02/084405 and WO 03/012549. Writing devices of this type are also referred to as laser lithography units whereas lithographic systems.